1. Field of the Invention
The present invention relates to an electro-optical device and a semiconductor device, and more particularly, to the structure of a connecting portion including a contact hole used for an electro-optical device or a semiconductor device.
2. Description of Related Art
In an electro-optical device, such as a display device, provided with a liquid crystal display device or EL (electro-luminescence) elements, or in a semiconductor device, a plurality of elements such as transistors and diodes forming, for example, a predetermined circuit and a plurality of wiring lines to connect these elements to each other are formed on a substrate. Such wiring lines mainly adopt a structure where the wiring lines formed of two conductive layers disposed on and under an insulating film are connected to each other through a contact hole (for example, Japanese Unexamined Patent Application Publication No. 7-326666). The related art structure of such a connecting portion is illustrated in FIGS. 6(a) and 6(b).
As illustrated in FIG. 6(a), in a connecting portion 60, a horizontally extending first wiring line 61 is connected to a vertically extending second wiring line 62 through a contact hole 63, disposed in a portion where the first wiring line 61 crosses the second wiring line 62. Further, a wiring line 64 extending substantially parallel to the second wiring line 62 on the right side of the connecting portion 60 is an adjacent wiring line formed in the same layer as the first wiring line.
FIG. 6(b) is a cross-sectional view taken along the plane A-A′ of FIG. 6(a). As illustrated in FIG. 6(b), a first insulating film 66 and a second insulating film 67 are sequentially laminated on a substrate 65. The first wiring line 61 is formed on the second insulating film 67. A third insulating film 68 is formed on the second insulating film 67 to cover the first wiring line 61. Further, the contact hole 63, that penetrates the third insulating film 68 and reaches the surface of the first wiring line 61, is formed above the first wiring line 61. The second wiring line 62 is formed in the contact hole 63 to contact the first wiring line 61 on the bottom surface of the contact hole 63. As a result, the wiring lines 61 and 62 are electrically connected to each other.
In the related art two-dimensional structure of FIG. 6(a), the end of the first wiring line 61 and the edge of the second wiring line 62 coincide in plan view. Therefore, in consideration of the design rule determined by the photolithography technology used or, by the exposure apparatus used, when the minimum space between patterns formed in the same layer is referred to as S, the gap between the end of the first wiring line 61 and the edge of the adjacent wiring line 64 is S. The gap between the edge of the second wiring line 62 and the edge of the adjacent wiring line 64 is also S. Therefore, it is not possible to further narrow the gap between the edge of the second wiring line 62 and the edge of the adjacent wiring line 64, which extend in parallel with each other. In an electronic device such as a liquid crystal display device and a semiconductor device, it is necessary that the elements be minute and highly integrated. Such a requirement cannot be met by the above-described structure of the connecting portion.
For example, in a liquid crystal display device in which a peripheral circuit is included, in an input and output wiring portion to sample a video signal, as the number of bits increases, the number of video signal lines extending in parallel with each other increases. The number of contact holes between a second conductive layer and the video signal lines significantly increases. Accordingly, the area occupied by the input and output wiring portion increases.